1. Field of the Invention
The present invention relates generally to the field of electrical circuit interrupters for electrical power transmission and distribution, and more particularly to a method and arrangement for minimizing electrical field stress on circuit interrupters and their housings via the arrangement of the external sheds or skirts of the housing.
2. Description of the Related Art
Various circuit interrupters are known for the electrical power transmission and distribution field. For outdoor application, the insulating housings of these circuit interrupters include external sheds or skirts to satisfy desired power-frequency voltage withstand ratings in a variety of environmental conditions. As the diameter of such housings is decreased, high electric field stresses inside of the housing also appear on the exterior of the housing. At the desired BIL (basic insulation level) rating, the external electric field stresses must not exceed the breakdown level of air or other specified environment.
Accordingly, it is a principal object of the present invention to provide a method and arrangement for minimizing electrical field stress on circuit interrupters and their housings via the arrangement of the external sheds or skirts of the housing.
It is another object of the present invention to provide a grouping of external sheds on either side of the open gap defined by the open contacts of a circuit interrupter.
It is a further object of the present invention to provide a housing for a circuit interrupter that reduces the electrical field stress on the exterior of the housing via the grouping of sheds around the open contracts of the circuit interrupter.
These and other objects of the present invention are efficiently achieved by the provision of a method and arrangement for minimizing electrical field stress on circuit interrupters and their housings via the arrangement of the external sheds or skirts of the housing compared to a uniform spacing off the external sheds or skirts. In one arrangement, some of the sheds are grouped about each side of the open gap that is defined by the contacts of the circuit interrupter in an open position, i.e. increasing the leakage distance per unit length of the housing around the open gap compared to the middle of the open gap and other areas of the housing.